1. Field of the Invention
This invention relates to fluidic oscillators. More specifically, the invention is a fluidic oscillator having frequency control features that allow the oscillator's frequency to be controlled independently of the oscillator's mass flow rate or amplitude.
2. Description of the Related Art
In the 1900s, fluidic oscillators were developed for use as logical function operators. More recently, fluidic oscillators have been proposed for use as active flow control devices where an oscillator's jet output is used to control a fluid flow (e.g., gas or liquid). FIGS. 1A-1C schematically illustrate the basic operating principles of a fluidic oscillator. Briefly, fluid flow 100 enters a fluidic oscillator 10 at its input 10A and attaches to either sidewall 12 or 14 (e.g., right sidewall 14 in the illustrated example) due to the Coanda effect as shown in FIG. 1A. A backflow 102 develops in a right hand side feedback loop 18. Backflow 102 causes fluid flow 100 to detach from right sidewall 14 (FIG. 1B) and attach to left sidewall 12 (FIG. 1C). When fluid flow 100 attaches to left sidewall 12, a backflow 104 develops in left hand side feedback loop 16 which will force fluid flow 100 to switch back to its initial state shown in FIG. 1A. As a result of this activity, fluid flow 100 oscillates/sweeps back and forth at the output 10B of oscillator 10.
For conventional fluidic oscillators, the frequency of the oscillations is directly dependent on the supply pressure and hence mass flow rate (or amplitude) of the oscillator. However, for practical applications, it is highly desirable to decouple the frequency and amplitude of the oscillator so that the frequency of the oscillator could be controlled independently of its amplitude. A frequency-decoupled fluidic oscillator could thus deliver desired mass flow rates without changing the frequency or could deliver desired frequency oscillations at desired mass flow rates.